FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
AC 43.13-1B | 8. Engines, Fuel, Exhaust, and Propellers | 1. Engines | 8-20. Magneto-to-engine Timing
9/8/98
AC 43.13-1B
8-20. MAGNETO-TO-ENGINE TIMING.
While the actual process of timing magnetos to
an engine is covered in the engine manufac-
turer’s technical manuals, the following gen-
eral procedures may be applied.
a. Before installing a new magneto, the
correct “E” gap setting specified by the mag-
neto manufacturer should be verified.
b. When setting or checking the mag-
neto-to-engine timing, always turn the crank-
shaft steadily in the normal direction of rota-
tion to eliminate any error caused by gear
backlash.
c. Recheck magneto-to-engine timing
after any point-gap adjustment, or after re-
placement of the breaker points.
d. Never advance the magneto timing
beyond the engine timing specification rec-
ommended by the engine manufacturer.
e. The possibility of a timing error ex-
ists if a timing indicator which attaches to the
propeller shaft or spinner of geared engines is
used. Engine timing specifications are always
given in degrees of crankshaft travel and can-
not be applied directly to geared propeller
shafts because of the gear ratio. Therefore, the
correct position of the propeller shaft, if used
for timing, must be determined by multiplying
the crankshaft timing angle in degrees before
top center (BTC) by the propeller gear ratio.
8-21.8-29. [RESERVED.]
Par 8-20
Page 8-17 (and 8-18)